bitcoin

This is well-worth reading (non-paywalled version). Here’s the opening:

Cryptocurrencies, although a seemingly interesting idea, are simply not fit for purpose. They do not work as currencies, they are grossly inefficient, and they are not meaningfully distributed in terms of trust. Risks involving cryptocurrencies occur in four major areas: technical risks to participants, economic risks to participants, systemic risks to the cryptocurrency ecosystem, and societal risks.

I haven’t written much about cryptocurrencies, but I share Weaver’s skepticism.

Ross Anderson has a new paper on cryptocurrency exchanges. From his blog:

Bitcoin Redux explains what’s going wrong in the world of cryptocurrencies. The bitcoin exchanges are developing into a shadow banking system, which do not give their customers actual bitcoin but rather display a “balance” and allow them to transact with others. However if Alice sends Bob a bitcoin, and they’re both customers of the same exchange, it just adjusts their balances rather than doing anything on the blockchain. This is an e-money service, according to European law, but is the law enforced? Not where it matters. We’ve been looking at the details.

Previous attempts to track tainted coins had used either the “poison” or the “haircut” method. Suppose I open a new address and pay into it three stolen bitcoin followed by seven freshly-mined ones. Then under poison, the output is ten stolen bitcoin, while under haircut it’s ten bitcoin that are marked 30% stolen. After thousands of blocks, poison tainting will blacklist millions of addresses, while with haircut the taint gets diffused, so neither is very effective at tracking stolen property. Bitcoin due-diligence services supplant haircut taint tracking with AI/ML, but the results are still not satisfactory.

We discovered that, back in 1816, the High Court had to tackle this problem in Clayton’s case, which involved the assets and liabilities of a bank that had gone bust. The court ruled that money must be tracked through accounts on the basis of first-in, first out (FIFO); the first penny into an account goes to satisfy the first withdrawal, and so on.

Ilia Shumailov has written software that applies FIFO tainting to the blockchain and the results are impressive, with a massive improvement in precision. What’s more, FIFO taint tracking is lossless, unlike haircut; so in addition to tracking a stolen coin forward to find where it’s gone, you can start with any UTXO and trace it backwards to see its entire ancestry. It’s not just good law; it’s good computer science too.

Lately on the internet, people in the world of Bitcoin and other digital currencies are starting to use the word “crypto” as a catch-all term for the lightly regulated and burgeoning world of digital currencies in general, or for the word “cryptocurrency” — which probably shouldn’t even be called “currency,” by the way.

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To be clear, I’m not the only one who is mad about this. Bitcoin and other technologies indeed do use cryptography: all cryptocurrency transactions are secured by a “public key” known to all and a “private key” known only to one party­ — this is the basis for a swath of cryptographic approaches (known as public key, or asymmetric cryptography) like PGP. But cryptographers say that’s not really their defining trait.

“Most cryptocurrency barely has anything to do with serious cryptography,” Matthew Green, a renowned computer scientist who studies cryptography, told me via email. “Aside from the trivial use of digital signatures and hash functions, it’s a stupid name.”

Matthew Green and students speculate on what truly well-designed ransomware system could look like:

Most modern ransomware employs a cryptocurrency like Bitcoin to enable the payments that make the ransom possible. This is perhaps not the strongest argument for systems like Bitcoin — and yet it seems unlikely that Bitcoin is going away anytime soon. If we can’t solve the problem of Bitcoin, maybe it’s possible to use Bitcoin to make “more reliable” ransomware.

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Recall that in the final step of the ransom process, the ransomware operator must deliver a decryption key to the victim. This step is the most fraught for operators, since it requires them to manage keys and respond to queries on the Internet. Wouldn’t it be better for operators if they could eliminate this step altogether?

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At least in theory it might be possible to develop a DAO that’s funded entirely by ransomware payments — and in turn mindlessly contracts real human beings to develop better ransomware, deploy it against human targets, and…rinse repeat. It’s unlikely that such a system would be stable in the long run ­ humans are clever and good at destroying dumb things ­ but it might get a good run.

One of the reasons society hasn’t destroyed itself is that people with intelligence and skills tend to not be criminals for a living. If it ever became a viable career path, we’re doomed.

Attackers held an Austrian hotel network forransom, demanding $1,800 in bitcoin to unlock the network. Among other things, the locked network wouldn’t allow any of the guests to open their hotel room doors.

I expect IoT ransomware to become a major area of crime in the next few years. How long before we see this tactic used against cars? Against home thermostats? Within the year is my guess. And as long as the ransom price isn’t too onerous, people will pay.

EDITED TO ADD: There seems to be a lot of confusion about exactly what the ransomware did. Early reports said that hotel guests were locked inside their rooms, which is of course ridiculous. Now some reports are saying that no one was locked out of their rooms.

Abstract: We present the first empirical analysis of Bitcoin-based scams: operations established with fraudulent intent. By amalgamating reports gathered by
voluntary vigilantes and tracked in online forums, we identify 192 scams and categorize them into four groups: Ponzi schemes, mining scams, scam wallets and fraudulent exchanges. In 21% of the cases, we also found the associated Bitcoin addresses, which enables us to track payments into and out of the scams. We find that at least $11 million has been contributed to the scams from 13 000 distinct victims. Furthermore, we present evidence that the most successful scams depend on large contributions from a very small number of victims. Finally, we discuss ways in which the scams could be countered.